I'm about to build a lean-to conservatory with dwarf wall. For various reasons a suspended floor makes more sense than a concrete floor. a) does it matter which way the joists run? I favour parallel to the house wall. b) is it ok to leave a compacted earth base underneath or must it be covered?
TIA.
Mine was a Wickes uPVC jobbie with a steel suspended floor. I wish I'd gone for solid now.
It was arranged as big square sections round the edge and one front to back across the middle. Then it also had smaller section steel joists front to back at approx 18" spacing. The instructions that came with it were :
Lay galvanised chicken wire across the joists to support fibreglass insulation under the floor. Lay insulation. Lay T+G chipboard flooring. I use the Screwfix 'Timbadeck' screws - they were brilliant! Use a decently powerful drill with a Pozidrive bit and they drill their own pilot hole and countersink into the chipboard, then drill and tap the steel, all in one go.
I laid PVC sheet on the bare earth/old slabs beneath the floor. When I fixed the cladding around the base I brought the edges up and fixed it to the outside of the frame. You won't have this with a dwarf wall.
The reason I wish I'd gone for solid was that between digging deep holes for the support pads the floor is suspended on, and the extra complexity and cost of the steel frame, it would have been just as cheap to get concrete. And then when the conservatory leaked (as they do at first...) one corner of the chip soaked through over the winter where we didn't see it, and I had to patch it up later :-(
Also we are out in the country and have had various wildlife finding it's way underneath and scrabbling about.
But overall it works fine now - warm enough, quite 'soft' to walk on (just a thin vinyl floor on top of the chip) and not noisy like I thought it might be. The conservatory is though, when it rains!
I would never build a suspended wooden floor if at all possible.
Either go for block and beam in concrete, or solid. Its so much more functional.
Then DPM, insulate to the ruddy hilt and screed.
THEN you can tack floorboards down...on battens if you want a 'springy' feel or glue direct to the screed.
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